1. Field of the Invention
This invention relates to release agents, and more specifically to release agents capable of imparting excellent release property to the back side of a base material of a tape or the like or to the front side of a release paper, said back side or front side being in a contiguous relation with an .adhesive surface in an adhesive-containing product such as an adhesive tape, an adhesive label or an adhesive seal.
2. Description of the Related Art
Conventional release agents usable for such purposes are known to include acrylic acid compounds containing one or more long-chain alkyl groups bonded thereto, high-molecular compounds such as polyesters and polyamides, and organopolysiloxane compounds. They are used to impart release property to the back side of an adhesive tape or adhesive sheet or to the front side of a release paper so that a release surface can be formed there.
Among these release agents, organopolysiloxane compounds are known to be superior in properties such as release property and residual adhesion.
These organopolysiloxane compounds, however, involve the problems that they are difficult to permit release by suitable force and they require high-temperature baking subsequent to their coating on base materials, thus making it impossible to use them for film-shaped, thermoplastic base materials. They are also accompanied by the problem that they cannot be applied to a wide variety of base materials due to insufficient adhesion to certain types of base materials.
Further, releasable polysiloxane compounds have a small surface tension, leading to the problem that no writing is feasible on their release surfaces. They are also accompanied by the problem that they often exhibit "a repelling phenomenon" upon coating a pressure- or heat-sensitive adhesive on their release surfaces and cannot hence form good coated surfaces.
As a method for overcoming such problems as described above, the present assignees have already proposed that the use of a silicone copolymer as a release agent permits low-temperature baking and provides excellent properties including high adhesion to base materials and good writing quality of release surfaces.